GC IV Commentary Series – The Role of Principles in IHL

Editors’ note: The following series considers ICRC’s 2025 updated Commentary on the Fourth Geneva Convention. Rosa-Lena Lauterbach, Liisi Adamson, and Sean Watts’s introduction to the series is available here.

Principles occupy a distinctive place in international law. They may constitute a source of legal obligations, express fundamental features of a legal system, underlie more specific rules, or guide their interpretation. Yet, the term “principle” also designates different legal phenomena whose nature, status, and functions should not be conflated. This is particularly relevant in international humanitarian law (IHL), where principles remain pervasive despite increasingly detailed conventional and customary rules.

The updated International Committee of the Red Cross (ICRC) Commentary on the Fourth Geneva Convention of 1949 (GC IV) provides an opportunity to revisit the role of principles in IHL. They appear throughout the updated Commentary’s interpretation of GC IV; some are expressly identified as such, while others underlie particular rules. They also operate at different degrees of generality, from principles underlying IHL as a whole to those specific to particular branches, notably the law of occupation.

This series contribution first distinguishes general principles of law, general principles of international law and general principles of IHL, before examining how the updated Commentary refers to, gives expression to, and relies upon principles in interpreting GC IV.

Different Kinds of “Principles” in International Law

The notion of a “principle” is far from univocal in international law. Article 38(1)(c) of the Statute of the International Court of Justice (ICJ Statute) recognizes “general principles of law” as a source of international law. Beyond this formulation, however, doctrine distinguishes between general principles of law and general principles of international law. The distinction relates primarily to their origin: the former are derived from domestic legal systems and transposed into international law; the latter originate within the international legal order itself. Within this second category, principles may also develop within particular branches of international law, including IHL.

More generally, principles differ from specific rules in their degree of abstraction and mode of operation. While rules are ordinarily capable of more direct application, principles frequently require concretization through more specific norms.

General Principles of Law

Identification of general principles of law rests on a comparative process: different national legal orders are examined to determine whether they share a common legal principle. That process does not imply importing a particular domestic rule into international law; domestic rules are instead stripped of their specific technical or local features to identify the more general principle underlying them. A second step is then required. The principle must be capable of transposition to the international legal order.

This mechanism has traditionally been associated with the need to address gaps in international law and, in particular, to avoid situations of non liquet, in which a court would be unable to decide a dispute because no applicable rule of law could be identified. Indeed, the travaux leading to Article 38 of the ICJ Statute show that preventing non liquet was one of the purposes behind the inclusion of general principles, without granting the international judge a general power to legislate. General principles of law consequently perform a suppletive, rather than subsidiary, function. They may supply a legal solution where treaty and customary law leave a gap, but that does not translate to them occupying a hierarchically inferior position among the sources of international law.

International jurisprudence refers to numerous examples of such general principles, including res judicata, estoppel, the obligation to make reparation for a breach, the burden of proof, equality between the parties, lex specialis, and ne bis in idem. Many such principles concern procedure and the administration of justice, although general principles of law are not confined to procedural matters.

General Principles of International Law

General principles of international law, by contrast, do not originate in domestic legal systems or through the comparative process just described. They emerge from the international legal order itself. They may be derived as abstractions from treaties and customary international law and express fundamental norms inherent in the structure and functioning of the international community. Their identification therefore does not depend upon demonstrating that an equivalent principle exists across domestic legal systems, but upon its recognition and manifestation in international legal relations.

The characterization of such norms as principles rather than rules reflects their relatively high degree of abstraction and their importance to the legal system. They may underlie existing rules, provide coherence between them, and assist in their interpretation.

Yet importantly, these principles are not formulated with the same degree of generality. Some extend across international law as a whole, while others structure a particular branch of international law. General principles of IHL belong to this latter category.

Good faith is an apt example. As a general principle, good faith is expressed at a high level of abstraction. Its legal significance becomes more concrete through particular manifestations, such as the requirement to preserve the object and purpose of a treaty or, in appropriate circumstances, the legal consequences attached to prolonged silence or acquiescence. Equity and proportionality likewise provide examples of principles capable of finding different concrete expressions across the international legal order, including within particular branches of international law.

This should be distinguished from principles and methods specifically governing treaty interpretation, such as teleological interpretation and effectiveness, which may interact with the general principles discussed here but perform a distinct interpretative function.

General Principles of IHL

General principles of IHL are therefore principles specific to this branch of public international law and form part of the broader category of general principles of international law. They emerge from treaty and customary rules of IHL, whose underlying substance and rationale they express.

Their relationship with rules is particularly significant for present purposes. Generally speaking, principles of IHL are—like other general principles of international law—derived from existing rules, through a process of abstraction, whereby the common rationale underlying a number of specific norms is identified. At the same time, once identified, they may inspire, reinforce, and render those rules comprehensible, contribute to the coherence of IHL as a legal system and inform their interpretation. The relationship between principles and rules is therefore not unidirectional: principles may be extracted from rules while simultaneously illuminating the meaning and structure of those rules.

As with other principles of international law, principles of IHL do not operate at one uniform level. Among the others, humanity and military necessity are generally regarded as the foundational principles of IHL. They do not provide concrete behavioral guidance like other principles, such as distinction or precautions. Instead, they help explain the basic structure and rationale underlying the law of armed conflict. The principle of military necessity safeguards the pursuit of legitimate military objectives while subjecting military action to the limits imposed by IHL. Historically associated with a permissive conception according to which the necessities of war could prevail over legal constraints (“Kriegsräson geht vor Kriegsmanier”), military necessity is today understood as operating exclusively within the framework of positive IHL. It cannot justify conduct otherwise prohibited by the law and, conversely, limits permissible action to what is necessary to achieve a legitimate military objective.

Military necessity operates in two related dimensions. As a constitutional principle, it forms part of the foundations of IHL, whose rules reflect the accommodation between the necessities of war and humanitarian imperatives. As an operational principle, it functions within positive law both permissively and restrictively. It may authorize measures necessary to achieve a legitimate military objective where IHL so permits, while simultaneously limiting such measures to what is actually necessary for that purpose. The principle is therefore concretized in specific IHL rules and exceptions and cannot constitute an autonomous justification for departing from them.

The principle of humanity embodies the fundamental requirement of respect for the human person in all circumstances. It prohibits the infliction of unnecessary suffering, injury or destruction in the pursuit of a legitimate military objective and, more broadly, it establishes limits on armed violence and a minimum threshold of protection. As a general principle of IHL, humanity permeates the legal framework governing armed conflict and finds concrete expression in rules protecting civilians and persons hors de combat, requiring humane treatment and limiting means and methods of warfare.

Proportionality provides a particularly interesting illustration of the relationship between these different levels of generality. While proportionality operates more broadly as a general principle of international law, it also finds specific expression within IHL and can be identified as a principle of that body of law. It should not be reduced to the specific rule of proportionality applicable to attacks, as reflected in Articles 51(5)(b) and 57(2)(a)(iii) of Additional Protocol I. That rule constitutes one of the most prominent concretizations of the broader principle, whose manifestations extend beyond the conduct of hostilities and can be identified in numerous provisions of IHL. As I have argued in greater detail elsewhere, its manifestations extend beyond the conduct of hostilities and can be identified in numerous provisions of IHL.

The Presence and Role of IHL Principles in the Updated Commentary on GC IV

The updated Commentary frequently references principles in its interpretation of GC IV. This post’s limited analysis can only reflect on four provisions by way of illustration. Without seeking to provide an exhaustive account, the selected examples show how principles are expressed, concretized, and used to interpret individual provisions. The question is therefore not only which principles the Commentary identifies, but what work they perform in the interpretation of existing rules. As the examples below illustrate, their significance lies in helping to explain the rationale of its rules, determine their scope and limits, and guide their application to circumstances not specifically contemplated at the time of drafting.

Humanity and the Overarching Significance of GC IV, Article 27

In the Commentary’s 2025 edition, humane treatment assumes a central role in the interpretation of numerous detailed GC IV protections. The overall object and purpose of the Convention itself is identified as the protection of individuals during armed conflict (para. 42). Here, the authors refer specifically to the guarantees of humane and equal treatment embodied in GC IV, Article 27(1). These guarantees thus overarchingly contribute to the interpretation of the Convention, with a general provision informing the understanding of more specific rules. The principle as contained in Article 27 is therefore neither detached from positive law nor exhausted by a single rule. It is expressed throughout the Convention and retains broader interpretative relevance.

This broader interpretative role can also be observed in the Commentary’s treatment of other provisions. Its interpretation of GC IV Article 4 provides a particularly interesting example. More specifically, the Commentary moves beyond a strictly formal application of the nationality criterion in Article 4 by recognizing that, where a Party treats its own nationals as having allegiance to the adversary, they may exceptionally qualify as protected persons (paras. 1026 et seq.). In doing so, it extends the protection of Article 4 to individuals who would otherwise fall outside its personal scope on the basis of nationality alone.

The Commentary’s reliance on allegiance allows account to be taken of the relationship between an individual and the enemy while ensuring that persons falling within the Convention’s protective rationale benefit from the guarantees attached to protected-person status. This approach is consistent with the Convention’s protective object and purpose and may also be understood as reflecting the interaction between the principles of humanity and military necessity. Article 4 thus illustrates how principles, together with the Convention’s object and purpose, may guide the application of an existing rule to contempary factual circumstances.

This understanding is further explored in Eugenie Duss’s contribution to this series, particularly within the context of occupation by proxy.

Explicit Reliance on Principles: GC IV, Article 53

Article 53 of GC IV prohibits the destruction of property by an occupying power except where such destruction is rendered absolutely necessary by military operations. The updated Commentary construes this exception narrowly, requiring absolute military necessity and, even where such necessity exists, that the destruction remain proportionate to the anticipated military advantage (paras. 3369 et seq.). It expressly presents the provision as balancing the principles of humanity and military necessity, the latter finding concrete expression in the narrowly framed exception of destruction “rendered absolutely necessary by military operations.” Here, the Commentary combines absolute military necessity, a reasonable connection between the destruction and military operations, good faith, and proportionality between the destruction and the anticipated military advantage.

At the same time, the Commentary situates Article 53 within the more specific normative framework of occupation law by describing the prohibition of destruction as an expression of the conservationist principle (or principle of preservation of the status quo ante), which seeks to preserve, as far as possible, the situation and rights existing in the territory prior to occupation. It further relies on the broader legal principle of proportionality, requiring the occupying power, where destruction would otherwise be permissible, to resort to less intrusive measures whenever possible. In this respect, the principles invoked by the Commentary contribute to determining how far that exception extends.

Principles Specific to Particular IHL Regimes: GC IV, Article 64

Article 64 of GC IV concerns the continuity of the legal order in occupied territory and the circumstances in which an occupying power may alter it. The Commentary’s introduction expressly states that the provision “embodies principles fundamental to the law of occupation, including the conservationist principle” (para. 3717). The temporary nature of occupation and the absence of any transfer of sovereignty combine to form a concrete rule here, by which the existing legal and institutional order are preserved rather than reshaped according to the occupier’s preferences. The principle forms the backbone of a basic obligation to maintain the laws in force and constrains the exceptional legislative powers granted to the occupying power.

The Commentary gives this principle concrete effect in several ways. Suspension, for example, should be preferred to repeal where it is sufficient to achieve the legitimate purpose pursued (para. 3735), while permanent or far-reaching changes to the institutional structure of the territory are generally precluded (paras. 3773 et seq.). At the same time, the interpretation of GC IV, Article 64 reveals the interaction of the conservationist principle with necessity and proportionality. Legislative measures adopted for security purposes must be necessary, and the Commentary expressly considers that the requirement of necessity itself entails proportionality: such measures cannot exceed what is required. Article 64 of GC IV thus illustrates not only the presence of principles in the Convention, but also their interpretative function: principles of different degrees of generality interact to explain the rationale of the provision; delimit the powers it confers; and guide its application in concrete circumstances.

Conclusion

The updated Commentary confirms that principles remain an integral part of IHL notwithstanding the increasing specificity of its conventional rules. They do not constitute a homogeneous category, nor do they operate at a single level of abstraction. Foundational principles, such as the principle of humanity and the principle of military necessity, coexist with more specific principles, such as proportionality and, within the law of occupation, the conservationist principle. Closely connected to positive law, principles may underlie and find concrete expression in particular rules, while also helping to explain their rationale, determine their scope and limits, and guide their application to contemporary circumstances.

The 2025 Commentary may be understood as according particular weight to the principle of humanity, notably in light of its identification of the protection of individuals during armed conflict as the Convention’s overall object and purpose. This does not, however, mean that the principle of humanity is given absolute priority over the other principles underlying the Convention. In particular, the principle of military necessity plays an important role in the interpretation and application of its rules.

Nor is the importance accorded to the principle of humanity necessarily new: humanity was already deeply embedded in GC IV and its earlier interpretation, including the 1958 Commentary. What the updated Commentary reflects may therefore be less a new weighting of these principles than a particularly marked expression of the importance of the principle of humanity within an interpretative framework in which military necessity retains its relevance. This apparent priority of the principle of humanity must nevertheless be relativized by the continuing importance of military necessity. The coexistence of these two considerations preserves the pragmatic character of IHL, which is one of its strengths as a body of law designed to regulate the realities of armed conflict.

It is noteworthy in this respect that, although the principle of humanity occupies a foundational place in IHL, its precise legal status and autonomous normative function remain comparatively underexplored. In particular, questions persist as to the role it may play, independently of specific rules, in the interpretation and development of IHL. These aspects may therefore warrant further examination.

Most importantly, the role of principles cannot be captured solely by identifying provisions in which the Commentary expressly uses the term “principle.” Their influence may also be implicit, embedded in the structure and interpretation of individual rules. The updated Commentary thus reveals IHL as a legal framework in which principles and rules remain closely interconnected: principles are concretized through positive law, but continue, in turn, to explain its rationale, contribute to its structure, coherence and guide the interpretation and application of its rules.

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Anaïs Maroonian holds a Ph.D. in Law from the University of Geneva, with a research focus on international humanitarian law.

The views expressed are those of the author, and do not necessarily reflect the official position of the United States Military Academy, Department of the Army, or Department of Defense. 

Articles of War is a forum for professionals to share opinions and cultivate ideas. Articles of War does not screen articles to fit a particular editorial agenda, nor endorse or advocate material that is published. Authorship does not indicate affiliation with Articles of War, the Lieber Institute, or the United States Military Academy West Point.

 

 

 

 

 

 

 

Photo credit: U.S. Army, Army Sgt. Collin Mackall